Congress has until Tuesday to pass a spending plan, or else federal agencies will lock their doors, cutting off such services as passport approvals and food programs for low-income families.

One of the key problems: Democrats and Republicans have been arguing over President Obama's controversial health-care overhaul, the Affordable Care Act, that begins getting funded under the federal budget on Oct. 1.

The Republican-controlled U.S. House of Representatives passed a temporary budget to keep the government operating until Nov. 15, and included language to defund Obamacare. But the Democrat-controlled U.S. Senate is expected to pass a temporary budget today that eliminates the provision stripping money from the health-care law.

House Republicans — among the most vocal opponents of Obamacare — are unlikely to agree to the Senate's updated bill, making a shutdown more likely, but House Speaker John Boehner (R-Ohio) has said Republicans are still seeking to avoid closing the government.

Obama, meanwhile, has defended his health-care law, saying Republicans are trying to "blackmail a president" to stop it.

Gov. Chris Christie, a potential Republican presidential candidate in 2016, said Thursday in an interview to be broadcast on Sunday that Republicans who allow a shutdown to occur would be "irresponsible" — although he added that he expected Congress to reach an agreement.

Should a shutdown take place, whom would you blame: Obama, Senate Democrats, House Republicans, or are all of the parties involved at fault? Vote in the poll at right?